Selection system for circuits or electric equipment

ABSTRACT

A switching network has three cascaded stages, each stage including a number of sections. Means associated with the secondary stage tests the availability of links in the primary and tertiary stages. When a match of idle primary and tertiary links is found, in association with an idle secondary link, the network operates to complete a path through all three stages.

United States Patent [72] Inventors GeorgesA.Duval [54] SELECTION SYSTEM FOR CIRCUITS OR ELECTRIC EQUIPMENT 2 Claims, 10 Drawing Figs.

U.S.Cl 179/18 GF H04q 3/42 Field of Search l79/l8.74, 18.74 A, l8 BT Jl/BJCE/BBt PIE/MAE Y Jl/NC TOE) JfCT/O/VJ llli [56] References Cited UNlTED STATES PATENTS 3,349,189 10/1967 Van Bosse 179/18 (.74) 3,439,!25 4/1969 Boehm 179/18 (.74) 3,275,752 9/1966 Esperseth et al l79/l 8 GE Primary Examiner-- Kathleen H. Claffy Assistant Examiner-William A. Helvestine Attorneys-C. Cornell Remsen, Jr., Walter J. Baum, Percy P. Lantzy, J. Warren Whitesel, Delbert P. Warner and James B. Raden SELECTION SYSTEM FOR CIRCUITS OR ELECTRIC EQUIPMENT The present invention concerns a selection system for circuits or electric equipment, and, more particularly, a selection system making it possible to connect an individual equipment unit to a common equipment unit through a several stage connecting network. Such a system is applicable namely, though nonexclusively, in automatic telephone exchanges.

In a telephone exchange, every subscriber's line has at its end an individual equipment unit so-called subscriber's junctor which is able to detect the calls and to signal them to the common units in the exchange. These subscribers junctors are connected to the outlets of a connecting network which can be made up of three selection stages so-called primary stage, secondary stage and tertiary stage. In each stage, the selectors are grouped into sections. One section is made up of a group of selectors which have their homologous outlets multiplied. The subscribers junctors are distributed into groups, and, each group is connected to the outlets of a group of selectors of the primary stage, making up a primary section. Common equipment units, so-called feeders, are connected to the inlets of the switching network, that is to say to the inlets of the selectors of the tertiary stage. One inlet, and only one, of each primary section is connected to one outlet, and one outlet only, of a secondary section through a link so-called primary link. Thus a primary section can have access through, a single primary link to each secondary section and vice versa. Likewise, one inlet, and one inlet only, of each secondary section is connected to an outlet of a tertiary section through a link so-called secondary link. A secondary section can thus have access, by means of a single secondary link, to each tertiary section and vice versa. Between a primary section and a tertiary section there are, therefore, as many paths as there are secondary sections.

Each feeder has two accesses connected to two inlets of the tertiary stage, respectively. One of these accesses, socalled access calling-line-side, is provided for the connection of a calling line; and the other one, so-called access called-lineside, is provided for the connection of a called line. The feeder, as its name implies, has the function of feeding the calling and called lines with supply current. It also has the responsibility to transmit the ringing current along the called subscriber's line so as to keep operating his bell until he lifts his station receiver.

A call between two subscribers is established by first connecting the calling subscriber's line to the access calling-lineside of the feeder, through the connection network-and this constitutes the selection of the calling line; then, by connect ing the called subscriber's line to the access called-line-side in a similar fashion this constitutes the selection of the called line.

The invention concerns a selection system which makes it possible to connect an individual equipment unit (subscriber's junctor) to a common equipment unit (feeder) through a three-stage connection network; and this in simple, economical fashion.

One feature of the invention is a selection system for circuits or electrical equipment comprising namely: a switching network made up of a primary stage formed up by primary sections, of a secondary stage formed up by secondary sections, of a tertiary stage formed up by tertiary sections, these various stages being linked to one another in such way that between every particular section of a stage and every particular section of a neighboring stage there should only exist a single connection so-called link; lines ended each by an individual line equipment unit and connected each to an outlet of a primary section; common equipment units connected each to an inlet of a tertiary section; a system for selecting a path between a determined line and a common equipment unit, said system comprising: means for identifying the primary section and the outlet in that primary section to which is connected the said line, means for identifying the tertiary section and the inlet in the tertiary section to which is connected the common equipment unit, means associated with each secondary section and each made up of a switchable test circuit for simultaneously testing, on the one hand, the availability of a link between the identified primary section and the considered secondary section, and, on the other hand, the availability of a link between the secondary section and the identified tertiary section, so that, the test circuit indicates if these two links are simultaneously available or not, that is to say, if the connection path joining; the identified primary section to the identified tertiary section through the intermediary of the considered secondary section is available or not.

According to another feature of the invention, the test circuit associated with each secondary section is made up of a relay selectively connectable, on the one hand, to the link which connects one identified primary section to the secondary section, and, on the other hand, connectable to the link which connects that same secondary section to an identified tertiary section, through a decoupling circuit interdicting the transmission or potentials from one link upon another, the presence of a busy condition potential on one or the other of the links, preventing operation of the relay and marking that tested connection path is unavailable.

According to another feature of the invention, a choosing chain makes it possible to choose a path in the case where several test circuits have operated.

According to an alternative, another feature of the invention is a switching network designed in such fashion that there exist two links between any secondary section and any tertiary section; the path selection being then operated in two stages: during a first stage, each test circuit is connected to one of the two links, and then, if no path is available, during a second stage, each test circuit is connected to the other link.

Different other features of the invention will become apparent from the description that follows, given by way of nonlimiting example, in conjunction with the accompanying drawings comprising:

FIG. ll, a block diagram of the connections in a telephone exchange to which the present invention can be applied;

FIG. 2, the diagram ofthe first stage ofa switching network;

FIG. 3, the diagram of the second and third stages of a switching network which, assembled with the first stage of FIG. 2 will make up a three-stage switching network; as well as the essential means provided, according to the invention, for performing the selections in this network;

FIG. 4, the plan for assembling FIGS. 2 and 3;

FIG. 5, an alternative of the diagram of the second and third stages of a switching network, which, assembled with the first stage of FIG. 2 will make up an alternative of a three-stage switching network; as well as essential means provided, according to the invention, for performing the selections in this network;

FIG. 6, the plan for assembling FIGS. 2 and 5;

FIGS. 7, 8 and 9, assembled as shown by FIG. 10, are the detailed diagrams of a markers circuits enabling the putting into operation of the selection system, object of the present invention;

FIG. 10, the plan for assembling FIGS. 7, 8 and 9.

In referring to FIG. I, the description will first be given of a diagram of the connections in a telephone exchange to which the present invention can be applied. This exchange handles subscribers lines such as 13. These lines have at their ends, in the exchange, individual equipment units such as JA so-called subscriber's junctors. These junctors have as particular function to current-supply the lines when these latter are free, to detect the calls transmitted by the telephone stations and to have all this informed to a common unit, so-called marker.

The switching network RC comprises three selection stages (primary, secondary and tertiary). To the outlets of the network, that is to say to the outlets of the primary stage, are connected the subscribers junctors JA; and, to the inlets of the tertiary stage, are connected common units such as AL, socalled feeders. A feeder has two accesses: the access 10, socalled access calling-line-side, to which can be connected a calling line, and the access 1e, so-called access called-lineside, to which can be connected a called line. The feeder has for function to provide the supply current of the calling and called lines, to transmit the ringing current along the called subscriber's line, so as to keep the bell operating until the subscriber lifts his receiver, and, to isolate both accesses in order to operate the disconnection at the end of the call conversation. Moreover, the feeder can be connected to a common unit EN so-called register, which has mainly for function to transmit the dialing tone inviting the calling subscriber to dial and to receive the digits of the called number. Finally, the operation of the exchange is controlled by the marker MQ.

When the subscriber of a line, such as line lg, lifts his receiver the junctor .IA detects the call. The marker MQ identifies the output of the connection network to which is connected the line. It chooses a free-feeder, say for instance AL, and will thus know, consequently, the inlet of the connection network to which it is connected. It performs a selection between the identified outlet and inlet and then controls the connection. The line lg is connected to the access la of the feeder. Simultaneously, under control of the marker MO, the feeder AL is connected to a register such as EN. The marker MO releases. The register EN transmits a dialing tone to the calling line 13 subscriber and receives, in return, the number of the called line. When it has received that number, the register EN calls the marker MQ, seizes it and transmits to it the number of the called line for establishing the call conversation. The marker MQ knows therefore the identity of the called subscriber's line and, consequently, the outlet of the connection network to which it is connected. It then identifies the feeder AL and the inlet to which is connected its access l. It performs a selection between the identified outlet and inlet and then controls connection of called line to access 1e of the feeder AL. The marker MQ finally releases, whereas the feeder AL keeps sending the ringing current along the called line until the subscriber answers. When answer is made, the call is established under the sole supervision of the feeder.

By referring to FIGS. 2 and 3, assembled as indicated in FIG. 4, the description will now be given of an embodiment of the switching network RC of FIG. 1 as well as the essential elements of the selection system of the invention. FIG. 2 represents the first stage of the switching network, FIG. 3 represents the second and third stages as well as the selection means. In order to render the explanations easier, a numerical example will be used here, without of course it limiting the scope of the present invention.

According to this example, the exchange will handle 256 subscribers lines lg] to lg256 which are ended by the junctors .IAI to .IA256 respectively. They are distributed into l6 groups of 16 lines upon the outlets of l6 primary sections SP1 to SP16. Each primary section has therefore 16 outlets.

The secondary stage comprises eight secondary sections. Each of the primary sections is connected by a single link socalled primary link to each of the secondary sections. These links are referenced in the figure by a letter p followed by the primary section number and then by the secondary section number which they connect. Thus, the eight inlets of the primary section SP1 are connected respectively to the first out lets of the secondary sections SS1 to SS8 by the links p1.l to p1.8. The eight inlets of section SP2 are connected respectively to the second outlets of the secondary sections SS1 to SS8 by the links p2.1 to p2.8. The eight inlets of section SP16 are connected respectively to the last outlets of the secondary sections SS1 to SS8 by the links 116.1 to pl6.8.

The tertiary stage comprises four sections. Each tertiary section comprises as many outlets as there are secondary sections, same as each secondary section comprises as many inlets as there are tertiary sections. Each of the secondary sections is connected, by a single link so-called secondary link, to each of the tertiary sections. These links are referenced by the letter s followed by the secondary section number and then by the tertiary section number which they connect. Thus, the four inlets of the secondary section SS1 are connected respectively to the first outlets of the tertiary sections ST1 to ST4 by the links sl.1 to s1.4. The four inlets of the secondary section SS8 are connected respectively to the last outlets of the tertiary sections ST1 to ST4 by the links s8.l to s8.4.

The result is that between a primary section and the secondary stage there are as many links as there secondary sections. Between a tertiary section and the secondary stage there are as many links as there are secondary sections.

To the inlets of the tertiary stage are connected the feeders such as ALI to AL32.

The links of the connection network have at least three conductors: two line conductors and one signalling conductor. When a link enters into a connection, its signalling conductor is earthed by the common unit onto which this connection ends up. When a link is free, it will be considered being isolated.

Finally, the marker MQ of which certain elements only are shown in the figure, has a test and choosing circuit CTC enabling the testing and the choosing of a connection path between a primary stage outlet and an inlet of the tertiary stage, through the coincidence circuits D1 to D8, corresponding each to one of the secondary sections SS1 to SS8. The circuit D], for instance, is assigned to section SS1. Its left inlet can be connected to the links pl.l to 116.1 and its right inlet to the links sl.1 to s1.4.

It will be assumed that during a calling line selection, a calling line was connected to a feeder ALI, for instance, and, more precisely speaking, to the access la of that feeder. The register EN has received, from the calling subscriber, the number of the called line, say for instance the line 131. It has seized the marker MO and transmitted to it the number of the called line.

At selection of the called line, the marker must select a connection path between the access l of feeder ALI and the junctor 1A1 of the line Igl.

The marker identifies the access Ie' of feeder ALI and obtains its position which is characterized by the tertiary section (ST1 in the example taken here) and, in that section, by the inlet to which it is connected. 0n the other hand, the marker identifies, by means of the called line number (Igl), received from register EN, the position of that line, which defines the primary section (SP1) and, in that section, the outlet to which it is connected.

The marker must therefore select a path between the primary section SP1 and the tertiary section ST1. Contacts cpl.1 to cpl.8 corresponding to the primary section SP1 and contacts cl1.1 to (.118 corresponding to the tertiary section ST1 will close, controlled by means not shown in the figure, and connect the test and choosing circuit CTC, by the coincidence circuits D1 to D8, to the primary links and to the secondary links of the connection network. The circuit D8, for instance, is connected to the links p1.8 and s8.1. If the signalling wire of one or the other link is earthed, the circuit D8 provides a busy tone to the circuit CTC for indicating that the corresponding path is not free. Same applies for the seven other possible paths. The circuit CTC identifies the connection paths available between the section SP1 and the section ST1 and it chooses one, say for instance the path utilizing the section SS1. Then the marker controls the connection. The called subscribers line lgl is connected to the access !e' of feeder ALI through: line 131, subscriber's junctor .lAl, primary section SP1, sink p1.1, secondary section SS1, link sl.1, tertiary section ST1, access le'of feeder ALl.

By referring to FIGS. 2 and 5 assembled as shown in FIG. 6, an alternative of the switching network RC in FIG. 2 will now be described, with the provided corresponding arrangements, in the marker M0, for performing selections. FIG. 5 illustrates the second and third stages of the switching network as well as the selection means. As can be seen, the primary stage and its links with the secondary stage are unchanged.

Each secondary section is connected by two links to each tertiary section. Thus, between a determined secondary section and a tertiary section, there are two secondary links. For

instance, the secondary section 5811 is connected to the tertiary section STl by two links, links sl.1 and slLll. Likewise, the secondary section SS1 is connected to the tertiary section 5T4 by the links sdll, shl and shAl, shAl.

To every secondary section there is assigned a coincidence circuit Dll to Db; the circuit Dll, for instance, is assigned to the section SSll. Its left inlet can be connected to the links 211.11 to 1216.11, and its right inlet to the links sll.ll to sllAl and slLll to .rlmt.

It is assumed that, as previously, a connection is to be established between the primary section SH and the tertiary section STll. The marker performs first of all a first test identical to the preceding one. Contacts cplLll to cplfl corresponding to the primary section SP1, and, contacts crl.1 and ctllfl corresponding to the tertiary section STll close, controlled by means not shown in the figure and connect the circuit CTC, through the circuits D1 to Db, to the primary links and to the first group of secondary links. In each circuit Dl to D8, the availability of a primary link and of a secondary link is set into coincidence. In the circuit Dll, for instance, the availability of the link pll.ll is set into coincidence with the availability of the link sl.ll. If not a single one of the devices such as Dll responds positively to this test, the circuit CTC will be switched, by operation of contacts cult to cullfi, onto the other links connecting the secondary sections to the same tertiary section STll, and the same test will be performed again between the same primary links and the new secondary links. In the circuit D1, for instance, there is being set in coincidence the availability of the link 11.1 with the availability of the link sLll.

Referring to FIGS. 7, 8 and '9, the circuits will now be described which enable putting into operation the selection system of the present invention. The FIGS. 7, h and 9 must be assembled as indicated in FIG. 10. They correspond to a network RC such as the one of FIGS. 2 and 5 assembled, in which two links are provided between secondaries and tertiaries.

In these figures there are just shown the circuits of marker MQ, of register EN and of a feeder ALI, which are indispensable for understanding the present invention. The network RC is not shown in the figure and only the connections, between the marker and the various links, are indicated in FIG. 7 by a circle inside which is written the number of the link to which it leads. In FIG. 7 is found the testing and choosing circuit CTC, in FIG. it the marker control circuit, and in FIG. 9 the energizing circuits of the connection electromagnets.

The various circuits are realized by means of relays, contacts and diodes. A relay is illustrated by a rectangle bearing on either side the connections ofa winding. it is referenced by two small letters followed by a number, in the case of homologous relays. According to the detached contact representation, the contacts controlled by a relay are arranged anywhere in the three FIGS. 7, 8 and 9. Indeed, since these three figures form up a whole and represent the circuits of marker MO, certain contacts of a relay placed in one figure may happen to be in another figure. These contacts bear the reference symbol of the relay followed by a number. Thus, reference ctlkltl designates the contact lit), placed in FIG. 9, ofctll, placed in FIG. it. Finally, it is worth mentioning that the various circuits are current-supplied by one same source of direct current, say a battery for instance, whose positive terminal is earthed. The circuits leading onto the negative terminal of that battery are ended by an arrow.

It will be assumed that, initially, a calling line (see FIGS. 2 and 5) is connected to an access la of feeder ALll and that this latter is connected to the register EN. The relay on of register EN and the relay st of feeder ALll are energized. The marker is available and all its relays are at rest condition.

Moreover, it is assumed that the register will have just received the number of the called line, say lgll for instance. The register seizes the marker by the application of an earth potential along the wire lk. This earth controls the energizing of the relay mg. The contact mgl closes and connects a general operation earth. In order to simplify the figure, the general earth circuit is illustrated by black circles; one will admit of course that they are all connected directly.

The relay tm energizes by means of contacts tzllll, csfi.]l,...cs ll.ll. The relay na energizes by means of contact nr2 and holds through its contact nall. The relays nb, nc, nd, ne, nf then energize successively through contacts n02, nb2, n02, nd2, n22. On the other hand, the register EN transmits to the marker M0, by means not shown in the figure, the called line number. This transmission is performed in an appropriate code, say for in- I stance a binary code; and this necessitates four transmission wires per digit. In the case of a three-digit number, the units digit is received on the relays ua/ud, along the wires lu; the tens digit is received on the relays da/dd, along the wires Id; and the hundreds digit is received on the relays ca/cd, along the wires lc.

The contacts of relays ua/ud, da/dd and salad are arranged in the form of decoding contact trees Fl and P2 so as to decode the called line number. The position of that line in the primary stage to which it is connected is thus identified. The contact tree lPll marks the relay designating the primary section to which the called line belongs. in the example taken here (line lgll) the section SP1 is concerned, and the cor responding relay cpl energizes through: battery, contact tree Pl, relay cpll, relay ta, earth. The relay ta energizes in series with the relay cpll so as to indicate that the identification of the primary section has taken place. These two relays hold through the contact cp1l.9. The contact tree P2 marks the relay designating the outlet in the precedingly identified primary section (SP1), to which is connected the called line. In the present example, it is the outlet ll that is concerned. The relay chll therefore energizes. The relay ck energizes in series with the relay chll so as to indicate that the identification of the outlet has indeed taken place and the two relays hold through the make contact chll.ll.

On the other hand, the marker must also identify the position of the feeder ALll in the tertiary stage to which its access called-line side is connected. For that purpose the contacts mg2 and mgfi are closed and they apply an earth along the wires lb and 1h respectively. The earth potential along wire Hz is retransmitted by contact cn2, of the register, to all the feeders. The feeder ALll retransmits it through its contact M2 and through means not shown in the figure, along a wire lg which is proper to it, to a relay which characterizes the inlet to which it is connected in the tertiary section. In the example taken here, the relay svll energizes. The relay sb energizes in series with the relay sv so as to indicate that the identification of the inlet, in the tertiary section to which is connected the feeder ALll, is done. The earth potential along the wire lb is retransmitted, by the contact 0111 of register EN, to all the feeders. The feeder ALll, which has its contact stll closed, retransmits it along a wire lj which is proper to it, to a relay ml to 014 corresponding to the tertiary section to which it is connected. In the example taken here, the feeder ALll is connected to the section STll and the relay ctl therefore energizes and will hold through its contact 011.9. The relay tb energizes so as to indicate that the identification of the section, to which the feeder ALll belongs, is done. The relay lb holds by its contact tbZ. Decoupling diodes preventing the transmission of earth potential from contact c119 onto the relays ct other than the relay all.

The contact tbll closes. The relay tz energizes through contacts rbll, tal, mvtl.ll,...mvll.ll and general earth. The contacts 121 to close, and this enables the operation of the testing and choosing circuit CTC. The contact 1110 operates. The relay tm is short-circuited but does not release.

The contacts cplLl to cpllfi are closed and connect respectively the links pl.ll to pill originated from the primary section SM and leading onto the various secondary sections SSl to 55$, onto the diodes dall to dail of the circuits Dll to D8. The contacts ct]l.ll to ctllfl connect respectively the links $1.11 to sill, originated from the tertiary section STll and leading onto the various secondary sections SS1 to SS8, onto the diodes dbll to dbfi of circuits D1 to D8. The diodes dal to dad and dbl to dbfi are associated by pairs so that each of these circuits might provide the coincidence of the availabilities of a link, connecting the primary section SP1 to a secondary section, and of a link connecting the same secondary section to the tertiary section STl; both links together making up a connection path between the primary section SP1 and tertiary section STl. The availability of each link is indicated by the absence of an earth along its corresponding signalling wire.

According to the above example, it is intended to test the availability of links pl.l to pl.8 and sl.l to $1.8. If, for instance, link p1.8 is busy, an earth is present along its signalling wire. This earth is retransmitted by the diode 1108 of the decoupling circuit D8 and it inhibits the battery provided by the contact 11.8. The corresponding relay cs8 cannot therefore energize. Likewise, if the link s8.l is busy, the busy condition earth is retransmitted, by the contacts 011.8 and 0141.8, to the diode db8 of circuit D8. This earth inhibits the battery of contact I28 and prevents the energizing of relay cs8. All the more so, if both links pl.8 and s8.l are busy, the relay cs8 cannot energize. Whereas, the coincidence of the absence of any earth potential on two links tested by the same circuit such as links pl.l and sl.l tested by the circuit D1 enables energizing of the corresponding relay cs-csl in the example taken here by the contact tzl.

Several relays cs can energize simultaneously. These relays designate the possible paths, and thus, as was already seen above, the utilizable secondary sections. The contacts csl.l to 8.! of these relays close, and this enables designating one secondary section, and only one, per each energizing of a determined relay mv. For instance, the relay cs1 has energized. The closing of contact csLl controls the energizing of relay mvl with designates the secondary section SS]. The relay mvl holds through its contact mvl.l. Operation of the contact mv1.l controls also the release of relay :2, and this indicates that the choosing of a secondary section, through which the call can be established, is indeed done. The relay rm is disshort-circuited and holds.

The marker is now in possession of all the information elements which make it possible to effect a connection between the line Igl and the feeder ALl. lt knows:

for the primary stage, the identify of:

' the primary section (SP1) to which is connected the line lgl (relay cpl the outlet of the primary section (SP1) to which is connected the line lgl (relay chi the inlet of the primary section SP1 connected to the selected secondary section and which corresponds to the identity of the secondary section (relay mvl for the secondary stage, the identity of:

the secondary designated section (SS1) (relay mvl the outlet of the secondary section SS1 connected to the primary section (SP1) and which corresponds to the identity of that primary section (relay cpl the inlet of the secondary section SS1 connected to the identified tertiary section (STD and which corresponds to the identity of that tertiary section (relay crl for the tertiary stage, the identity of:

the tertiary section (STl) to which is connected the feeder;

the outlet of the tertiary section STl connected to the secondary section SS1 and which corresponds to the identity of that secondary section (relay mvl the inlet of the tertiary section STl to which is connected the feeder (relay svl The marker also controls, by means not shown in the figure, the testing of the called line. This latter, supposed to be free, the relay di energizes by means not shown in the figure, the contact dil closes and the marker will control the establishing of the connection.

Establishing the connection is performed by closing an appropriate connection point in each primary, secondary and tertiary stage.

It will be assumed that every section of a stage is made of a crossbar multiswitch of a well-known type, such as the one described in the US. Pat. No. 3,529,113 issued Sept. 15, 1970 to Vazquez for Miniature Crossbar Switch with Flexible Tape Selecting Means and Mechanical Latch. This multiswitch comprises selection bars, corresponding to the outlets; connection bars corresponding to the inlets. The selection bars are controlled by electromagnets so-called selection electromagnets, and, the connection bars are controlled by electromagnets so-called connection electromagnets. To establish a connection between an inlet and an outlet, the connection bar corresponding to the inlet is set by the energizing of its connection electromagnet, in order to release any connection previously row wires as there are sections. For instance, the connection electromagnets VPl to VP8 and the selection electromagnets HP] to HPl6 of the primary section SP1 are connected to the wire of the upper row. The column wires are distributed into two groups. To each wire of the first group are connected the connection electromagnets having the same rank in the various sections. There are therefore as many column wires of the first group as there are connection bars in the primary sections. For instance, the electromagnet VPI of rank 1 in the section SP1 is connected to the wire of the first column; and the electromagnet VP8 of rank 8 is connected to the wire of the eighth column. To each wire established by that connection bar. Then is set the selection bar corresponding to the outlet, through energizing of its selection electromagnet, and then the connection bar is released (release of the connection electromagnet); and this has for effect to establish the connection between the inlet and outlet. Then the selection bar is released. The connection holds mechanically.

The connection electromagnets and the selection electromagnets of the multiswitches of one same stage are controlled by matrix circuits MP for the primary stage, MS for the secondary stage, MT for the tertiary stage. To each row wire, of the matrix MP, are connected the connection and selection electromagnets belonging to the same section. There are therefore as many of the second group are connected the selection electromagnets having same rank in the various sections. There are therefore as many column wires of the second group as there are selection bars in the primary sections. The electromagnets HP] to HP16, for instance, of the section SP1, are connected to the first and 16th column wires.

The matrices MS and MT are designed in the same fashion. However, in accord with the switching network shown in FIG. 5, two groups of column wires are provided for the connection electromagnets in the matrix MS; contacts 041.10 to cu4.l0 make it possible to pass from one group to the other. Likewise, two groups of row wires are provided for the selection electromagnets in the matrix MT, contacts cul.9 0144.9 making it possible to pass from one group to the other.

The energizing of an electromagnet is performed by applying an earth along a row wire and a battery onto a column wire. A decoupling diode is associated with each electromagnet. The establishing of the connections in the various stages is performed successively in the tertiary stage, the secondary stage and then the primary stage. This operation is controlled by a six-relay sequential circuit (na, nb, nc, nd, ne, nf).

The various preceding identifications having been performed, the relay m energized by the contacts m2, ck], sbl, rb3, lz9, nf3 and dil.

The contact nrl closes. The relay nx energizes through the following circuit: battery, relay nx, contacts nfZ, nrl, nb3, fc2, M3 and earth.

The contact nxl closes and controls the energizing of a connection electromagnet of matrix MT. In the example chosen here, the connection electromagnet VTl of section ST] energizes through: battery, contacts nxl, nbS, svl.2, decoupling diode, electromagnet VTl of section STl, contacts 011.11,...0! 4.11, earth.

The contact nx2 closes and relay ny energizes through contacts m2 and nx2.

The contact ny2 closes and controls the energizing of a selection electromagnet of the matrix MT. In the example chosen here, the electromagnet HTl of the section STl energizes through the circuit: battery, contacts ny2, nb4, mvl.4, decoupling diode, electromagnet l-lTl of section ST], contacts 0141.10, crl.ll...c14.l l, earth.

The contact nyl operates. The relay na releases whereas the relay nb holds through the contacts rib] and ny1. The contact n03 opens. The relay nx releases. The contact nx1 opens and removes the energizing battery from the connection electromagnet VT1. The electromagnet VTl restores to rest condition. The connection point inside the tertiary section ST1 is established. The feeder ALI is connected to the link s1.1 (see FIG.

The contact m2 operates and controls the release of relay ny which cuts the energizing battery from the selection electromagnet HT1 by opening of its contact nyZ. The electromagnet 1-lT1 restores to rest condition.

The contact nyll restores to its rest condition and breaks the circuit of the relay nb which releases. The contacts nb4l and M25 restore to their rest condition and rout the circuit of contacts m1 and nyZ onto the matrix MS (contacts nd5/6 operating). The relay nx energizes through: battery, relay nx, contacts nfll, nr1, nb3, nd3, na3,fc2, ne3, earth.

The contact nx2 operates, and controls the energizing of relay ny.

The contact ny2 closes and controls the energizing of the whereas the electromagnet of the matrix MT. ln the example chosen here, the electromagnet H81 of section SS1 energizes through: battery, contacts ny2, nb l, "d6, cp1.11, decoupling diode, electromagnet H81 of SS1, contacts mu1.3,...mv8.3, earth.

The contact nyl. operates. The relay nc releases whereas the relay nd holds through the contacts 11:11 and ny1. The contact nc3 opens. The relay nx releases. The contact nx1 opens and removes the energizing battery from the electromagnet VS1. This latter restores to rest condition. The connection point inside the secondary section SS1 is established and the primary link pll.1 is connected to the secondary link s1.l (see FIG. 5).

The contact nxZ operates and controls the release of relay ny which cuts the energizing battery from the selection electromagnet H81, by opening of contact nyZ. The electromagnet H81 restores to rest condition.

The contact ny1 restores to its rest condition and the relay nd releases. The contacts ndS/fi restore to their rest condition and thus rout the circuits of contacts nxl and ny2 onto the matrix MP. The contact nd4 closes and controls the energizing of the relay nx throughzbattery, relay nx, contacts nj2, nr1, nb3, mi l, n03, na3,fc2 and ne3.

The contact nxl closes and controls the energizing of a connection electromagnet of matrix MP1. According to the example taken here, the electromagnet VPll of primary section SP1 energizes through: battery, contacts 11x1, nbS, nd5, mvLZ, decoupling diode, electromagnet VP1 of SP1, contacts cp1.10,... 01216.10, earth.

Contact nx2 closes and the relay ny energizes. The contact ny2 closes and controls the energizing of the selection electro-magnet. For instance, the electro-magnet lllPl of SP1 energizes through: battery, contacts ny2, nb t, nd6, ch1.2, decoupling diode, electro-magnet MP1 of SPI, contacts 0 21.10 cp16.10, earth. Contact nyl operates and controls the release of elay ne,

and the latter controls the release of relay nx through the opening of contact M3. The contact nx1 opens. The connection electromagnet VPll restores to rest condition. A connection point is established in the primary stage. The line lg1 is connected to the link pl.1 (FIG. 2) and, thus, the line [g1 is connected to the feeder AL1 through: line Igl, section SP1, link pl.1, section SS1, link sl.1, section ST1, feeder AL1.

Contact m2 operates and controls the release of relay ny which cuts the energizing battery from the selection electromagnet H1 1 by opening of contact ny2. The electromagnet HP1 restores to rest condition. The contact ny1 restores to its rest condition, and this determines the release of relay nf. The contact nf l closes. The end of connection relay fc energizes and applies, by its contact fcll, an earth along the wire If onto the register EN in order to control the release of this latter. The relay cn releases. The register removes the earth from wire 1k. The relay mg releases and disconnect the general operation earth. All the relays of the marker MO release and the marker is released.

Establishing the connection process is terminated. The line [g1 is connected to the access I of feeder AL], and, by the feeder, to the calling line.

In the above description, it was assumed that the first group of tested secondary links enabled establishing a connection. lf no path is available, that is to say if no relay cs is energized, at the end of a certain time, the relay tm releases in order to control the testing and choosing of a path by utilizing the second group of secondary links. The relay rb holds by its contact 2. The contacts lml to tm ll close and connect the relays cull to 0144 to the wires lj. [n the example considered here, the relay cull corresponding to relay ct1 energizes. The contacts 011.] to 0141.8 operate and rout the diodes db1 to dbl; of the decoupling circuits D1 to Dd onto the links s1.1...,r'l.ll. The testing and choosing circuit performs then the testing and choosing of a path made up of a primary link (p111, for instance) and of a secondary link (s 1.1, for instance). This testing and choosing are performedl by energizing a relay es and a relay mv (cs1 and mvll for instance). The connection is then made as before, by the energizing and then restoring to rest condition of a connection electromagnet and of a selection electromagnet in each matrix, by marking the appropriate row wires and column wires. it is worth noting that in the matrix MT, the row wire of the connection electromagnets is marked by a contact Cl (contact 0:111, for instance) and, the row wire of the selection electromagnets is marked by a contact ct and a contact cu operating (c1111, cu1.10, for instance). In the matrix MS, the column wire of the connection electromagnets is marked by a contact ct and a contact cu operating (11.10 and culfi, for instance).

It is understood the foregoing description of a specific embodiment of this invention is made by way of example only and is not to be considered as a limitation on its scope. All nu merical details are provided to facilitate the descriptions and may vary with every case of application of the present inventron.

SUMMARY The invention concerns a selection system for circuits or electrical equipment comprising, namely: a switching network made up of a primary stage formed by primary sections, of a secondary stage formed by secondary sections, of a tertiary stage formed by tertiary sections, these various stages being connected one another in such way that between any particular section of a stage and any particular section of a neighboring stage there should exist only one connection so-called link; lines ended each by an individual line unit and connected each to an outlet of a primary section; common units connected each to an inlet of a tertiary section; a system for selecting a path between a determined line and a common unit. This system comprises means for identifying the primary section and the outlet in that primary section to which is connected the said line, means for identifying the tertiary section and the inlet in that tertiary section to which is connected the common unit, means associated with each secondary section and made up each of a switchable test circuit for simultaneously testing, on one hand, the availability of a link between the identified primary section and the concerned secondary section, and, on the other hand, the availability of a link between the secondary section and the identified tertiary section, so that the test circuit will indicate whether these two links are simultaneously available or not, that is to say if the connection path joining the identified primary section and the identified tertiary section, passing through the considered secondary section, is available or not.

We claim:

1. A selecting system for a switching network comprising three cascaded stages providing alternate paths through said network, each of said stages having a plurality of switching sections, line circuit means associated with the outlets of a tertiary stage, means for interconnecting the inlets and outlets of said three stages so that there is only one possible connection in each stage for any given one of said alternate paths through each relay connected to a primary stage outlet and the other side of said winding connected to a tertiary stage inlet, decoupling means between the relays of said plurality for isolating operating circuits to said relays.

2. The system of claim 1, further comprising chain circuit means for selecting between said relays when several alternate paths test idle.

I I t I I 

1. A selecting system for a switching network comprising three cascaded stages providing alternate paths through said network, each of said stages having a plurality of switching sections, line circuit means associated with the outlets of a tertiary stage, means for interconnecting the inlets and outlets of said three stages so that there is only one possible connection in each stage for any given one of said alternate paths through said stages, means associated with the central of said three stages for identifying the sections of said primary and tertiary stages including the end points of a desired switch path, a plurality of links interposed between stages, means for testing the links for the availability of idle paths through said secondary switch, means for selecting a path where availability is indicated for each of said three stages, said selecting means comprising a plurality of relays with one side of the winding of each relay connected to a primary stage outlet and the other side of said winding connected to a tertiary stage inlet, decoupling means between the relays of said plurality for isolating operating circuits to said relays.
 2. The system of claim 1, further comprising chain circuit means for selecting between said relays when several alternate paths test idle. 